Fuel Use

The results of field testing the POCA/Maputo Ceramic Stove (MCS) and traditional metal stoves (TMS) using an uncontrolled cooking test (UCT) are attached. In a UCT people cook whatever they want and we watch carefully. The results have fuel-moisture compensated values. The charcoal was almost always hardwood lumps. Larger meals tend to be watery and small meals tend to be frying something in oil.

The comparison indicates a clear change in relative performance with meal size. The bigger the meal, the more the savings with the improved stove. There is also a chart attached showing the increase in thermal efficiency with meal size.

The meal size on one the X-axis.

The WBT locates one point on the line. Performing the test seven times locates that point very accurately but is it difficult to know where the line goes from that point.

No ‘outliers’ were removed in this analysis even when they were obvious. The meal size varies with the season so the question about consumption has more than one answer.


The Kitengela Arboretum Promoting sustainable agro-energy technologies and conservation education. Kenya Seeds of Change An initiative contributing towards national afforestation through direct seeding of woodlots. Concept Compiled by: Teddy M. Kinyanjui Sustainability Consultant Kitengela Arboretum Po. Box 23058 Lower Kabete Nairobi, Kenya. April 2009

**Kenya Seeds of Change**
The degraded state of Kenya’s national and private forests (and therefore, the overall environmental health of the country) borders on the point of no return. Unless large scale forestry efforts are undertaken by both the public and private sector in the next few years, the damage that has been done to the countries forests will become irreversible. Due to the slow pace of natural regeneration of forests (as compared to their exploitation), a boost is sorely needed to meet current and future demands by Kenya’s ever growing population for sustainably grown wood by-products, especially the charcoal and firewood that is used daily by 80% of the country’s population.
The Kenya Seeds Of Change initiative aims to contribute towards national afforestaion by land owners through the countrywide sales of inexpensive tree seeds and the promotion of direct seeding woodlot establishment. Seeds are by far the best method of promoting wide scale tree planting in Kenya. These are some of the benefits from the direct planting of tree seeds compared to planting seedlings:

  • Seeds are Cheaper! (At roughly 0.25cents per tree compared to 20+ shillings per seedling)
  • The tree’s hardiness and survivability increases.
  • Thousands of seeds can be transported and stored much more easily then thousands of seedlings can until the planting time comes.
  • Seeds can be massively disseminated through existing retail outlets with minimal price increments from producer to consumer. Tree seedlings face problems of availability at the right time, dissemination logistics etc.
  • Partially domesticated indigenous tree species are best grown from seed. They are already adapted to Kenya’s climate, soils and pests and the trees are currently widely used and understood by the population.
  • Seeds simplify the enhancement of the genetic diversity of planted woodlots.
  • The above/below ground biomass ratio is more conducive to healthy growth when a tree is planted from seed.
  • Overall financial losses and risks from drought, animals etc. are significantly less under direct seeding.

Limited Access to Good Seed

  • From large commercial plantations to small scale rural and urban farmers, the access to purchase certified tree seeds according to their growing zones and uses is extremely limited to anyone who would like to plant trees.
  • Currently the only place to buy graded, certified tree seeds is at KEFRI (The Kenya Forestry Research Institute), located in Muguga, on the outskirts of Nairobi.
  • In contrast all the Nakumatt and Uchumi supermarket chains and all of the Agro-Vets in small or large towns and cities stock a variety of seeds ie. sukuma wiki (Kale) and maize etc.
  • Which of course raises the question; why don’t they all stock small packages of tree seeds that are suited to their market base?

This is what the Kenya Seeds of Change initiative has been started to get done.

Stoves Camp 2010, Cottage Grove Oregon

Stoves Camp ParticipantsStoves Camp Participants

Fifty two high energy participants attended Stove Camp this year at Colgan’s Island, camping near the river, making and testing stoves, and listening to Fred’s Big Band harmonize so beautifully. Fred and his volunteers cooked breakfast every morning and dinners at nighttime parties on Rocket and TLUD institutional stoves.

Nick Salmons from International Lifeline Fund made a very successful Haitian charcoal stove that was voted “Best in Class” by his peers!

Stove Camp provides a venue for a gathered scientific community to advance knowledge of biomass cook stoves. Participants made new stoves and tested them daily for fuel use and emissions. Every morning the test data was shared and new stoves were constructed.

This year, a great deal of progress was made on charcoal stoves for Haiti. Camp participants, some of whom have worked in Haiti,designed a two-hour Water Boiling Test for Haiti, which uses a Haiti pot
and mimics a typical cooking task, cooking rice and beans. Charcoal stoves were constructed that used less fuel and produced less carbon monoxide compared to traditional Haitian stoves.

See the attached Stoves Camp Report for details of the tests, the interesting findings about the optimum charcoal to use for each stove, and pictures of the stoves tested.

As the United States biomass thermal and power industry continues to expand, new reliable technologies offering higher efficiency solutions must be introduced. The newly introduced EOS series biomass gasification boiler is among the most energy efficient of AESI’s high-performance, low-maintenance biomass energy plants. The EOS series provides thermal outputs ranging from 600,000 BTU/hr to 20 million BTU/hr, and can be staged to provide increased capacity.

Designed and built by the leaders in the biomass waste to energy market in Europe, Uniconfort, the EOS series builds upon over 50 years of experience and over 4000 successful installations throughout the world. When asked about the highly efficient EOS series, CEO of Uniconfort Davis Zinetti notes, “we must not forget that greater efficiency is associated with less CO2 production. Choosing EOS, therefore, means making a choice in favor of the environment.”

Insights Into Fuel Efficiency and the Dissemination of Mud and Ceramic Stoves in Southern Africa
Peter Scott, Biomass Energy Consultant, December 23, 2007
Lorena 2 Pot 2003Lorena 2 Pot 2003

Shielded One Pot 2003Shielded One Pot 2003
Dear all

I wanted to offer a couple of brief insights into the recent dialogue regarding fuel efficiency and the dissemination of mud and ceramic stoves in southern Africa

First, A little back ground:

I worked with GTZ-EAP in Uganda for 3 weeks in August of 2003 . During that time I built a number of metal and brick stoves - both household and institutional - as well as bread ovens and a number of insulated ceramic combustion chambers . I didn't design the 2 pot Lorena stove but I did offer some suggestions on its design .

When I arrived GTZ had already begun developing prototypes for the two pot 'rocket ' Lorena mud stove as well as a single pot shielded mud stove. I made a number of recommendations: that they insulate the combustion chamber of the 2 pot stove and follow some simple rocket stove principles (shelf under fire, internal rocket elbow geometry, insulation, and proper gaps for optimal heat transfer).

2 pot Rocket Lorenas in Kampala
A number of tests of these stoves were performed by GTZ using the original WBT/PHU testing protocol (GTZ-EAP has the test data and the specific results so Im hoping that Leonard Magerwa might post the test data - Leonard are you out there?) during 2003

From my recollection the results looked something like this:

2 pot 'insulated' Rocket Lorena. Three versions were constructed and tested:
a.. -with pumice combustion chamber
b.. with 50/50 vermiculite c combustion chamber
c.. -with sawdust clay (unfired/non ceramic)

All of these stoves had very similar test results , something like slightly
above 30% PHU

2 pot mud rocket Lorena
a.. This stove performed slightly worse , something like 28% PHU

Single pot shielded fire mud stove
a.. This single pot stove had similar performance to the 'insulated' 2 pot stove. Around 30%. (sorry that's the best picture I have. Leonard , do you have a better one?)

Note: These 'lab' results are from the stove testing site that was set up in Kampala. They were built to exact specifications (stove built around 2 standardized pots and a 1 cm gap around both pots). As Dean and Tom pointed out, the stoves that were tested by USAID were most likely not constructed as per the original specifications nor were they used in the manner they were intended ( i.e. pots not submerged)

a.. The 'Insulated' versions all produced similar results in overall
efficiency even though they offer a spectrum of insulation quality : from
relatively high quality insulative materials such as pumice to a lower
quality insulative material such as unfired clay ceramic model .

a.. There was only a few percentage points of efficiency gained by
insulating the 2 pot stove

a.. Given the similarity of the results of the insulated stoves we could
conclude that in terms of fuel efficiency , the insulation of the
combustion chamber does not have a great impact on overall efficiency ie
reduction in fuel consumption. ( One would imagine that they had an improved
combustion efficiency, Unfortunately emission testing equipment was not
available during these tests but it did appear that the insulated stoves
were producing less visible smoke than the non insulated version)

a.. The un-insulated single pot chimneyless shielded fire proved to have
a similar efficiency as an insulated 2 pot chimney stove

Although these tests obviously aren't definitive they do point in a
certain direction which seem to support what Aprovecho has been saying for some time:

a.. Optimizing Heat transfer is important for reducing fuel consumption.
This means : using a skirt and/or tapering the slope underneath the pot so
that it reduces cross sectional area by .75 X

a.. Insulating the combustion chamber will have a greater impact on
improving combustion efficiency than it will on heat transfer and fuel

a.. With out standardization we can expect high performance or consistent

GTZ-EAP for a number of reasons - that they could elaborate upon - decided to promote the 2 pot Rocket Lorena ( my understanding is that the insulated version is promoted where possible, but due to poor access to materials,
it is the un-insulated version that is often produced in the field

When the stoves were designed it was recognized that they would face some significant dissemination challenges:

a.. Design drift. without proper tools and training the local producers
would not be able to produce the stove to the exact specifications of the

a.. Material substitution. Many owners would not be able to afford the
metal chimney that was needed for optimal use of the stove. Instead local
producers often made shorter chimneys out of mud that were difficult or
impossible to clean and very slow to generate draft due to their higher
mass .

a.. User 'error' Users using different size pots and not submerging the
pot into the stove. This would obviously decrease heat transfer , increase
fuel consumption and lead to increased smoke in the kitchen ie not produce
similar tests results as those produced at the Kampala test site.

The 2 pot sunken pot Rocket stove has been a meaningful experiment ( I would like to acknowledge The staff at GTZ_EAP (Phillipe Simonis, John Kutesakwe and Leonard Magerwa ) have worked very hard to produce a large quantity of stoves in a relatively short time period ( 50,000+ in 3 years)

Way forward?

Any household stove project is going to be faced with many challenges. How do we bring fuel efficient stoves to the people who can least afford them but need them the most?. How do we bring standardized stoves , which require technical ability , accurate tools and perhaps even advanced materials to these users. Who is going to pay for them if the users cant? It seems that that CDM mechanisms and factory production are one option for delivering
stoves to the poorest.

Of course, one avenue that has not been fully explore din Africa is dissemination of the single sunken pot shielded fire mud stove. Given the results of the testing done in Kampala in 2003 , it seems that there is potential for this stove to save fuel . Of course there is still plenty of opportunity for that stove to be poorly built and used.. Although given that it doesn't require two pots for it to work , nor an expensive chimney there is the chance that it could fill a certain niche in the stove world.

I can envision multiple shielded fire stoves being constructed in and outside of the house . Each stove sized to a specific pot. Since the stoves would be very low cost , the users could build many stoves as needed.

Its is an exciting time in the household stove world. We still have not come up with a fuel efficient stove and dissemination strategy to bring stoves to poor households in Africa. Its going to take a lot of trial and error , and
fumbling around in the dark to work out how to do this.

Laboratory Testing of Rocket Stoves of Various Capacities As Compared to the Three Stone Fire
Dean Still, Nordica MacCarty, Aprovecho Research Center, April 2007

In an effort to understand the relationship between stove capacity and fuel use and emissions the performance of three sizes of rocket stoves were compared.


The stoves were tested with the 2003 UCB revised Water Boiling Test. Pots that were integral to the stoves were used without a lid. Kiln dried Douglas fir at approximately 10% moisture content was burned in all tests. Only one test was performed on the household stoves. Therefore, results are not statistically valid but should be useful for general comparison. The [attached] graphs show results from three Rocket type stoves as compared to a carefully tended Three Stone Fire.

Btu Calculator

desc=Excel sheet by Ken Smith. Water boil and Btu

A great Excel sheet pertaining to different species of wood.


Dean Still on Stove Performance Tests and Chris Adam's Proposed Boiling Time Factor Test

Biomass Energy Conversion Factors
USDOE Biomass Feedstock Program ORNL

The following are links to Web sites we have found useful (many universities worldwide maintain good guides and conversion calculator pages):

160 grams of charcoal boils and simmers 5 liters/CF04 Stove
Lanny Henson www.lanny.us July 2, 2006

The CF04 Stove boiled and simmered 5 liters using only 160gr of charcoal and wood.

After several modifications to 4 different prototypes, it only took 150 gr of lump charcoal with 11% moisture and 10gr of wood to boil 5 liters of 83 degF/28.3 degC water in 45 min. That is 32 grams per liter to boil and simmer. At 1 hour after boiling the water was still simmering at 100 degC and after 2 hours the water was 205degF/96 degC. At this point I shut the air control and capped the pot module to stop the airflow and retain heat.

At 3 hours the water temp was 190 degF/87.8 degC and was 178 degF/ 81 degC at 4 hours.


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